Nuclear quadrupole resonance (NOR) techniques lend themselves readily to the determination of the charge distributions in various sigma, pi, and lone-pair orbitals in molecules. The technique requires the presence in the molecules of one or more atoms having a nuclear electrical quadrupole moment. Fortunately, a very large number of the biologically important compounds such as the purines, pyrimidines, amino acids, thiazines, barbiturates, etc. contain one or more nitrogen atoms whose nucleus does have a quadrupole moment. An extensive study of such nitrogen-containing molecules of biological importance is in progress, with current work dealing primarily with C-Nitro compounds, uracils, purines, barbiturates, phthalocyonenes, phenothiazines, and liquid crystals. Theoretical quantum mechanical calculations of charge distributions have been carried out by other researchers for a large number of molecules, but most of the calculations deal only with pi-electron distributions. Further, the calculations differ strongly among themselves, and correlations of the computed distributions with biological activity or with other parameters that are sensitive to the electron distribution (e.g. the Hammett sigma parameter) show significant disagreements for some compounds. The charge distributions determind by NQR studies can be used to improve these correlations, and to develop correlations where none are currently available.